Composite article

ABSTRACT

The invention relates to a composite structure including a plurality of fabric layers of interlaced flexible stretch-resistant strand material impregnated with a rigid resinous material and positioned in spaced generally parallel relationship to each other. A plurality of elongated partitions are disposed between adjacent layers and divide the space between adjacent layers into a plurality of elongated generally parallel channels. The partitions each comprise a plurality of stretch-resistant strand material interlaced with adjacent layers in a plane generally perpendicular to the adjacent fabric layers and are also impregnated with a rigid resinous material. In one embodiment, a rigid foamed material can be disposed in the channels for particular applications. A preferred method of making the rigid composite structure is also presented.

This application is a continuation-in-part of application Ser. No.350,304 filed 11 May 1989 now U.S. Pat. No. 4,914,836.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The present invention relates to composite articles formed frominterlaced stretch-resistant flexible strand material impregnated with arigid material and to the method of making such articles.

2. Description Of Prior Art

Typical prior art composite articles generally comprise a honeycombsandwich construction having a honeycomb core formed of a metal foilsuch as aluminum or aluminum alloys laminated between a pair of inneradhesive sheets and outer face sheets. Such laminated sandwichstructures have the disadvantage of being subject to delamination whensubjected to interlaminar stresses such as shear or tensile stresses.Delamination results in weakening of such laminate structures.

Accordingly, a principal desirable object of the present invention is toprovide a new and improved composite article of manufacture whichovercomes the disadvantages of the prior art comprising layers ofinterlaced stretch-resistant flexible strand material impregnated with arigid cured thermosetting resinous material and held in spaced relationfrom each other by a plurality of partitions disposed between the layersand dividing the space between the layers into a plurality of channels,the partitions being formed of stretch-resistant strand materialimpregnated with the same rigid resinous material.

Another desirable object of the present invention is to provide anarticle of manufacture having a high strength to weight ratio andimproved compression loading.

Another desirable object of the present invention is to provide anarticle of manufacture having a high damage tolerance.

Another desirable object of the present invention is to provide acomposite structure having improved resistance to shear and tensilestresses.

Another desirable object of the present invention is to provide acomposite structure which is readily adaptable to form an integral partof articles which require high strength to weight ratios.

Another desirable object of the present invention is to provide a newand improved method of producing such articles of manufacture.

A still further desirable object of the present invention is to achievethe above desirable objects with an essentially simple structure,lending itself to inexpensive mass-production.

These and other desirable objects of the invention will in part appearhereinafter and will in part become apparent after consideration of thespecification with reference to the accompanying drawings and theclaims.

SUMMARY OF THE INVENTION

In accordance with the present invention a composite structure meanshaving high strength to weight ratio and improved damage tolerance andwhich can be formed to selected configurations is provided which is, forexample, useful in the fabrication of articles for aircraft, spacecraft,seacraft, sporting equipment, automotive and, packaging and insulationmaterials. The composite structure of the present invention generallyenvisions at least a double plush-like mesh structure having at leastfirst and second layers (or a plurality of layers) of interlacedstretch-resistant flexible strand material positioned adjacent eachother, and defining an intermediate space between the adjacent firstlayer and second strand layers. A plurality of elongated interlacedpartitions are disposed between the first and second strand layers anddivide the intermediate space between adjacent strand layers into aplurality of elongated generally parallel channels. The partitions eachcomprise a plurality of pile stretch-resistant strand materialinterlaced with the first and second layers in a plane generallyperpendicular to the first and second layers. The channels formed by thelinking of the first and second layers by the pile partition strandshave a generally rectilinear configuration. Resiliently-compressiblesingle cell fluid-impermeable tubular members are disposed or integratedduring fabrication within all or at least a majority of the channels andadaptable to be inflated under fluid pressure to within the confininglimits of the channel walls, which are each defined by adjacent strandpartitions and the portions of the first and second strand layers withinthe adjacent partitions. The layers of interlaced stretch-resistantstrand material forming the partitions are impregnated with athermosetting resinous material which is curable to form a hard rigidstructure. The invention contemplates embodiments wherein the tubularmembers may be removed or may be thermosealed to the channel structuresdepending upon the use of the composite structure as discussed in moredetail herein. The invention also contemplates a multilayered structure.

As briefly stated the preferred process of making the rigid compositestructure of the present invention comprises the steps of: forming atleast a double plush interlaced structure having adjacent spaced layersof interlaced flexible stretch-resistant strand material and a pluralityof elongated partitions disposed between said adjacent layers anddividing the space between adjacent layers into a plurality of elongatedgenerally parallel channels; the partitions each comprising a pluralityof stretch-resistant strand material interlaced with adjacent strandlayers in a plane generally perpendicular to the spaced adjacent strandlayers; integrating during fabrication inflatable tubular members intothe channels; impregnating the interlaced layers and partitions with athermosetting resinous substance; inflating the tubular members to theconfining limits of the containing channels while subjecting thecomposite structure to sufficient pressure so as to form a matrix of theresinous substance about the strand material, removing excess resinousmaterial; and heating the composite structure to the thermosettingtemperature of the resinous material to cure the same and form a rigidmatrix of the interlaced strand material and cured thermosettingresinous material. The tubular members may then be removed or sealed tothe structure channels. The channels or open sealed tubular members canbe filled with a stiff or rigid foam material for particularapplications of the composite structure. In an alternate process where arelatively small composite structure is to be formed, the process iscarried out in a pressure vessel so that a high pressure is employedduring the sealing of the ends of the tubular members and thereafterduring the impregnation of the resin whereby the tubular members are ina relatively collapsed state during sealing and impregnation andthereafter the pressure is sufficiently reduced prior to the resincuring process whereby the tubular members are expanded to the confininglimits of the channels in which they are positioned to form an erectcomposite structure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of thepresent invention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings whereinlike reference characters denote corresponding parts throughout severalviews and wherein:

FIG. 1 is a fragmentary perspective view illustrating a structureembodying the principals of the present invention;

FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view of a structure similar to that of FIG.with the structure impregnated with a resinous material and furtherillustrating the tubular members in an inflated condition under fluidpressure and also showing the sealed ends of two of the tubular members;

FIG. 4 is a schematic representation of the structure of FIG. 3 andfurther illustrating one embodiment of the process of curing theresinous material while maintaining a desired configuration of thestructure;

FIG. 5 is a perspective view of the cured rigid composite structure ofFIG. 4 and additionally illustrates a multilayered or laminatedcomposite as shown by the dotted lines; and

FIG. 6, A, B and C, schematically illustrate examples of alternateconfigurations of the structure embodying the principals of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

Referring now to the drawings and particularly to FIGS. 1 and 2, thereis shown an embodiment of the basic structure means embodying theprincipals of the present invention. As illustrated, the structure,indicated generally by the numeral 10, comprises a double plush meshconstruction having a first or upper fabric layer 12 and a second orlower fabric layer 14, each formed of interlaced stretch-resistantflexible strand material 16. A plurality of elongated partitions orpiles 18 formed of stretch-resistant strand material 20 are providedwhich connect or interlace with the first and second strand layers in aplane generally perpendicular to the planes of the first and secondstrand layers 12 and 14 respectively. Adjacent partitions (for example18a and 18b of FIG. 2) together with the portions 12a of the upper layer12 and 14a of the lower layer 14 between the partitions 18a and 18b eachhave a generally rectilinear configuration and form elongated channelsor pipes 22 having a generally square or rectangular shape.

Suitable materials for forming the strand layers 12 and 14 and thestrand partitions or perpendicular piles 18 are stretch-resistant orfully drawn materials such as polyesters, nylon, polypropylene,polyethylene, fiberglass, carbon velvar, ceramics and the like.Additionally, conventional processes (and equipment therefor) such asweaving and knitting can be employed to form the intimate interlacedunified structure 10 of the present invention.

There are disposed or inserted into the chambers 22, during thefabrication process, flexible, expandable, fluid impermeable tubularmembers 24. The tubular members can, for example, be formed of a heatsealable elastomer which is impermeable to gaseous fluids. In apreferred embodiment the thickness of the tubular wall is selected inrelation to the material forming the tubular member so that the tubularmember is expandable to the confining limits of the channels 22 (as bestseen in FIG. 3) to maintain the structure in the erected ornon-contracted condition during resination of the layers and partitions.

While it is not essential that tubular members be provided for allchannels, which in part may be determined by the use of the structureand the level of action to be encountered, it is preferable that atleast a majority of the chambers be filled with the tubular members.

In the case where the tubular members are to be maintained in aninflated condition after the resinous material is cured, the gaseousfluids which can be employed to fill the pressurized tubular members 24of the structure 10 should preferably be a gas which will not diffuseappreciably through the walls of the tubular member material.

The two most desirable gases have been found to be hexafluorethane(e.g., Freon F-116) and sulfur hexafluoride.

Other gases which have been found to be acceptable, although not as goodas hexafluorethane and sulfur hexafluoride, are as follows:perfluoropropane, perfluorobutane, perfluoropentane, perfluorohexane,perfluoroheptane, perfluorocyclobutane, octafluorocyclobutane,hexafluoropropylene, tetrafluoromethane (e.g., Freon F-14),monochloropentafluoroethane (e.g., Freon F-115), and other Freon gasesknown as Freon 114, Freon 113, Freon 13 B-1, and Freon 13. It is to beunderstood that while the foregoing gases are preferred, other gasessuch as air, oxygen, nitrogen and mixtures of such gases can beemployed.

Referring more particularly to FIG. 3, the structure indicated generallyby the numeral 30 includes the basic structure 10 of FIG. 1 and furthershows the tubular members 24 in the sealed and inflated pressurizedstate. Each end of the tubular members is sealed as shown at 26 to forma single cell fluid-impermeable member 24. Additionally, as mentionedherein, the elasticity of the tubular members 24 is selected includingthe thickness of the tubular wall 28 so that when the tubular member issufficiently inflated under gaseous pressure or under vacuum it expandssufficiently and conforms generally to the shape of the channel walls tomaintain the structure in a straight, erect, non-collapsedconfiguration. The structure (first and second layers and partitions) isthen impregnated with a thermosetting resinous substance 32 to form acomposite layer of the resin and strand material indicated respectivelyby the numerals 12R, 16R and 18R in FIG. 3. A suitable thermosettingresin can, for example, be an epoxy resin.

One advantage of the inflated and pressurized tubular members 24 in theprocess of forming the composite structure of the present invention isthat the resin material is removed or forced out of the channels wherebythe channels are substantially relatively free of resin prior to andduring the resin curing process step. This step provides for a compositestructure having a relatively low resin to strand material ratio as wellas a higher strength to weight ratio.

Referring now to FIG. 4, there is illustrated a preferred method ofcuring the resin impregnated structure. As shown, the resin impregnatedand inflated structure 30 of FIG. 3, for example, is inserted into atool member indicated generally by the numeral 34 having a pair ofholding members 36 and 38 which are movable by arm members 40 and 42.The composite structure holding members 36 and 38 are provided with aplurality of apertures 44 which permit the composite structure to besubjected to positive and negative ambient pressure values. The toolmember 34 containing the composite structure 30 is placed within thechamber 46 of the metal vessel 48 (represented by the dotted lines). Thevessel 48 is provided with conventional means 50 which can serve to heatthe chamber in addition to providing selected positive or negativepressure values within the chamber 46. The composite structure 30 ismaintained at an appropriate temperature to effect curing of theresinous material and to form a hard matrix of the cured thermosettingresinous substance converting the interlaced strand layers andpartitions to a hard, light weight, rigid structure.

In preparing the composite structure for subsequent use in formingselected articles, the tubular members can be; a) retained in thechannels and pressurized as shown in channels 1 and 2 of FIG. 4; b)removed as shown in channel 3 (by melting or dissolving, for example);or c) laminated by thermosealing to the channel walls as shown inchannel 4. It is to be understood that the invention contemplates theinsertion of a stiff or rigid foam material in structures b and c wheresuch foamed material enhances the use of the structure.

As an alternate method of forming the composite structure, the ends 26of the tubular members 24 can be sealed under positive gas pressurewithin the vessel 48. The apertures 44 provide and insure that thecomposite structure 30 and contained tubular members are subjected tosuch external pressure. Thereafter the resin impregnated structure 30 issubjected to sufficient vacuum or negative gas pressure to expand thetubular members to the confining limits of the channel as discussedherein. Thereafter the resin curing process and disposition of thetubular members is carried out as described herein.

Referring now to FIG. 5, there is illustrated a cured resinous compositestructure 52 similar to the structure 30 of FIGS. 3 and 4 but with thetubular members removed. The composite structure 52 includes first andsecond layers 54 and 56, partitions 58 and channels 60. A secondstructure 52A shown by the dotted lines can be laminated to structure 52to form a multilayered composite structure. In this respect, it is to beunderstood that in the initial formation of the interlaced structure ofthe present invention a triple plush or multi-layer structure can beformed as well as the double plush structure.

As illustrated in FIGS. 6A, 6B, and 6C the structure 30 can be formedinto various three dimensional configurations such as the curvedconfiguration shown at 6A. The curved configuration can be provided byproviding a curved tool member 34 for the resin curing step. As shown at6B the structure 54 is provided with an overall tapered configuration bydecreasing the height of the partitions 18R. In the circularconfiguration shown at 6C the length of the inner layer 12R isfabricated to be shorter than the length of the outer layer 16R so as toform the circular configuration. The present invention also contemplatesthe filling of one or more of the channels with a stiff or rigid formingfoam material 62 as shown in FIG. 6A which can be polyurethane or otherfoam material. The foam material provides added strength as well asincreased overall volume to the structure with minimum weight increasethereby increasing the buoyancy feature of the structure which rendersthe structure suitable in the construction of water craft.

While the invention has been described with respect to preferredembodiments, it will be apparent to those skilled in the art thatchanges and modifications may be made without departing from the scopeof the invention herein involved in its broader aspects. Accordingly, itis intended that all matter contained in the above description, or shownin the accompanying drawing shall be interpreted as illustrative and notin limiting sense.

What is claimed is:
 1. A composite structure having a high strength toweight ratio and providing improved resistance to delamination, saidcomposite structure comprising:a plurality of fabric layers ofinterlaced flexible stretch-resistant strand material; said fabriclayers each being impregnated with a thermosetting rigid formingmaterial; said fabric layers being positioned in spaced generallyparallel relationship to each other; and a plurality of elongatedpartitions disposed between adjacent fabric layers and dividing thespace between adjacent fabric layers into a plurality of elongatedgenerally parallel channels; said partitions each comprising a pluralityof stretch-resistant strand material interlaced with adjacent fabriclayers in a plane generally perpendicular to said adjacent fabriclayers, each of said partitions being impregnated with a thermosettingrigid forming material.
 2. The composite structure of claim 1 whereinsaid rigid material is a cured thermosetting resinous substance.
 3. Thecomposite structure of claim 1 wherein at least a majority of saidchannels contain a foamed material.
 4. The composite structure of claim3 wherein the foamed material is polyurethane.
 5. The compositestructure of claim 1 wherein tubular members are contained within atleast a majority of said channels.
 6. The composite structure of claim 1having a generally tapered configuration.
 7. The composite structure ofclaim 1 having a generally circular configuration.
 8. A rigid compositestructure comprising:a first layer of interlaced flexiblestretch-resistant strand material impregnated with a thermosetting rigidforming material; a second layer of interlaced stretch-resistantflexible strand material impregnated with a thermosetting rigid formingmaterial and positioned adjacent said first layer and defining anintermediate space between said first layer and said second layer; and aplurality of elongated partitions disposed between said first and secondlayers and dividing said intermediate space into a plurality ofelongated generally parallel channels; said partitions each comprising aplurality of stretch-resistant strand material interlaced with saidfirst and second layers in a plane generally perpendicular to said firstand second layers, said partitions being impregnated with athermosetting rigid forming material.
 9. The rigid composite structureof claim 8 wherein said rigid material is a cured thermosetting resinousmaterial.
 10. The rigid composite structure of claim 8 wherein saidchannels contain a foamed material.
 11. The rigid composite structure ofclaim 8 wherein tubular members are contained within said channelmembers.
 12. The rigid composite structure of claim 8 wherein at least aportion of the configuration of the composite structure is non-linear.13. The rigid composite structure of claim 8 wherein the second layer ofinterlaced stretch-resistant strand material is shorter than the firstlayer and forms the inner layer of a composite structure having acircular configuration.